The thalassemia syndromes are inherited disorders of human hemoglobin synthesis characterized by absent or decreased synthesis of alpha or beta globin chains of normal adult hemoglobin (Hb A: alpha2beta2). The ability to make radioactive DNA copies (cDNA) by viral reverse transcriptase of the separate alpha and beta globin messenger RNAs (mRNA) and to use these cDNAs in qualitative or quantitative molecular hybridization assays for detection of alpha and beta globin gene DNA and/or mRNA have resulted in the demonstration of a number of different molecular defects in different forms of thalassemia. In some forms, globin gene deletions have been demonstrated whereas other forms are characterized by grossly intact globin genes which result in the production (or accumulation) of either no globin mRNA (some cases of beta -thalassemia), quantitatively deficient globin mRNA beta plus-thalassemia), or nonfunctional globin mRNA (other cases of beta-thalassemia). With the availability of newer molecular biology techniques such as improved molecular hybridization assays using recombinant globin plasmid cDNAs as probes, gel blotting techniques, nucleotide sequencing techniques, erythroid cell culture techniques, and recombinant DNA technology, we propose to carry out the following studies: 1) gene mapping by restriction endonuclease and gel blotting analysis of total cellular DNA in various forms of thalassemia to identify the extent of globin gene deletions in deletion mutants and search for globin gene structural abnormalities in nondeletion mutants; 2) nucleotide sequence analysis of thalassemic cytoplasmic globin mRNA and nuclear globin mRNA precursors; 3) analysis of thalassemic globin mRNA half-life and precursor globin mRNA processing in RNA labeling experiments using thalassemic bone marrow cells and/or differentiating thalassemic erythroid cell cultures; 4) isolation of thalassemic globin by recombinant DNA technology followed by structural analysis and in vitro functional testing of the purified thalassemic globin gene DNA.